Crystallization of 4′-epidaunorubicin hydrochloride

ABSTRACT

4′-epidaunorubicin hydrochloride is provided in a crystalline form which is stable and readily soluble. A process of producing the crystalline form includes crystallizing 4′-epidaunorubicin hydrochloride in a solvent system including (a) solvent A selected from C 1  and C 2  halogenated solvents and mixtures thereof, (b) solvent B selected from C 1 -C 5  straight and branched alcohols and mixtures thereof, and (c) solvent C selected from C 1 -C 5  straight and branched alcohols and mixtures thereof, wherein solvent C is selected to provide lower solubility to 4′-epidaunorubicin hydrochloride than solvent B.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Section 371 of International Application No.PCT/EP2010/005498, filed Sep. 8, 2010, which was published in theEnglish language on Mar. 17, 2011, under International Publication No.WO 2011/029576 A1 and the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates to crystalline 4′-epidaunorubicinhydrochloride and a process for the production thereof.

Anthracyclines comprise a large group of naturally occurring bioactivecompounds. Several anthracyclines are used in clinics as anticancerchemotherapeutic drugs. Examples of clinically important substances aredaunorubicin, doxorubicin, idarubicin, epirubicin, pirarubicin,aclarubicin, caminomycin, and zorubicin. Anthracyclines can be producedeither by chemical synthesis or by fermenting microorganisms. They areused as such (for example, aclarubicin, daunorubicin and caminomycin) orare semi-synthetic derivatives of other anthracyclines (such asepirubicin, idarubicin, doxorubicin, pirarubicin, and zorubicin).Anthracyclines are effective against leukemia and various solidcancerous tumors. Worldwide, the most used anthracyclines aredoxorubicin and epirubicin. Epidaurorubicin is the key-intermediate inthe synthesis of epirubicin.

U.S. Pat. Nos. 4,112,076; 4,345,068; 4,861,870; 5,945,518; and 5,874,550disclose the preparation of epirubicin hydrochloride and its use as ananticancer agent.

Currently, the major method for purifying 4′-epidaunorubicinhydrochloride is amorphous precipitation thereof from a solution byaddition of an antisolvent. Usually, in this method, a basic solution ofepidaunorubicin is treated with methanolic hydrochloric acid to adjustthe pH value in a range between 2 and 5, and subsequently4′-epidaunorubicin hydrochloride is precipitated by addition of anether.

U.S. Pat. No. 4,345,068 discloses precipitation of 4′-epidaunorubicinhydrochloride from a chloroform extract using methanolic hydrochloricacid. Although referred to as “crystallization,” this process does notproduce crystalline, but amorphous 4′-epidaunorubicin hydrochloride.

Boivin et al., “Substitutions of allylic esters: preparation of3-aminoglycals and their acid-catalyzed glycosidation. Use in thepartial synthesis of glycosides of the anthracycline group,”Carbohydrate Research, 79 (2):193-204 (1980) disclose precipitation of4′-epidaunorubicin hydrochloride from ethanol/ether. This process hasalso been found to produce amorphous, not crystalline 4′-epidaunorubicinhydrochloride.

Amorphous precipitation of 4′-epidaunorubicin hydrochloride, however,has the drawback that the precipitated 4′-epidaunorubicin hydrochlorideis only purely soluble and often purified unsatisfactorily.

BRIEF SUMMARY OF THE INVENTION

Therefore, the problem to be solved by the present invention is theprovision of a simple process for the purification and crystallizationof 4′-epidaunorubicin hydrochloride, which allows for 4′-epidaunorubicinhydrochloride to be crystallized in a form in which it is stable andreadily soluble.

This problem is solved by a process for crystallizing 4′-epidaunorubicinhydrochloride which process comprises crystallizing 4′-epidaunorubicinhydrochloride in a solvent system including:

-   -   a) solvent A which is selected from the group consisting of C₁        and C₂ halogenated solvents and mixtures thereof;    -   b) solvent B which is selected from the group consisting of        C₁-C₅ straight and branched alcohols and mixtures thereof; and    -   c) solvent C which is selected from the group consisting of        C₁-C₅ straight and branched alcohols and mixtures thereof,        wherein solvent C is selected to provide lower solubility to        4′-epidaunorubicin hydrochloride than solvent B.        By this process, crystalline 4′-epidaunorubicin hydrochloride is        produced.

The method of the present invention makes use of 4′-epidaunorubicinhydrochloride as a starting material. The origin and the form of4′-epidaunorubicin hydrochloride are not further restricted. Forexample, 4′-epidaunorubicin hydrochloride can be used which is producedfrom precursors in a preceding chemical synthesis. Also, commerciallyavailable 4′-epidaunorubicin hydrochloride can be used which is to befurther purified. It is also possible to use 4′-epidaunorubicinhydrochloride which is produced by use of suitable microorganisms andconverted into the corresponding hydrochloride in a subsequent step. Inparticular, it is possible to use as a starting material4′-epidaunorubicin hydrochloride which contains impurities, for example,impurities which are the result of preceding synthesis steps.

4′-epidaunorubicin hydrochloride is crystallized in a solvent systemcomprising solvents A, B and C which differ from each other. Therefore,the solvent system referred to herein comprises at least three differentkinds of solvents.

Solvent A is selected to have the capability to dissolve4′-epidaunorubicin hydrochloride. As for its structure, solvent A isselected from the group consisting of C₁ and C₂ halogenated solvents andmixtures thereof. Solvent A can be a single solvent or a mixture ofsolvents, but is preferably a single solvent. Generally, as solvent Aevery kind of solvent can be used as long as it has one or two carbonatoms, comprises at least one halogen atom and is suitable to dissolve4′-epidaunorubicin hydrochloride. Preferably, solvent A contains 1-3 andmore preferably 2 or 3 halogen atoms. As halogens, chlorine and bromineare preferred. The halogen atoms can be the same or different. Forexample, solvent A can be a compound which has at least one chlorineatom and/or at least one bromine atom. It is preferred that the halogenatom(s) present in solvent A is a (are) chlorine atom(s). The compoundor compounds used as solvent A can contain further functional groups inaddition to the halogen atom(s). On the other hand, it may be preferredthat solvent A does not contain such further functional group(s).According to a preferred embodiment, solvent A is a saturated compoundand thus does not contain a double bond. It can furthermore be preferredthat solvent A has only one carbon atom. Preferably, solvent A isselected from the group consisting of, dichloromethane, dibromomethane,chloroform, bromoform, dichloroethanes (such as 1,1-dichloroethane or1,2-dichloroethane), dibromoethanes (such as 1,2-dibromoethane),trichloroethanes (such as 1,1,1-trichloroethane or1,1,2-trichloroethane), tetrachloroethanes (such as1,1,2,2-tetrachloroethane), and mixtures thereof. More preferably,solvent A is selected from chloroform, dichloromethane and mixturesthereof.

Solvent B is selected on its ability to purify 4′-epidaunorubicinhydrochloride from common impurities. It is selected from the groupconsisting of C₁-C₅ straight and branched alcohols and mixtures thereof.Solvent B can be a single solvent or a mixture of solvents, but ispreferably a single solvent. Every alcohol having a C₁-C₅ carbonskeleton can be used as solvent B, as long as it is able to allow forpurification of 4′-epidaunorubicin hydrochloride. In particular, solventB can be a monoalcohol or a polyalcohol. Furthermore, solvent B includesalcohols having further functional groups in addition to the hydroxylgroup(s). It may be preferred, however, that solvent B have no furtherfunctional groups. Furthermore, it may be preferred that solvent B is asaturated compound and therefore does not contain double or triplebonds. According to a preferred embodiment, solvent B is selected fromthe group consisting of C₁-C₃ straight and branched alcohols andmixtures thereof. According to a further preferred embodiment, solvent Bis selected from the group consisting of C₁ straight and branchedalcohols, C₂ straight and branched alcohols, C₃ straight alcohols andmixtures thereof. Most preferably, solvent B is selected from the groupconsisting of methanol, ethanol, 1-propanol and mixtures thereof.

Solvent C is selected to be an antisolvent to 4′-epidaunorubicinhydrochloride. It is selected from the group consisting of C₁-C₅straight and branched alcohols and mixtures thereof. Solvent C can be asingle solvent or a mixture of solvents, but is preferably a singlesolvent. Solvent C is also selected to provide lower solubility to4′-epidaunorubicin hydrochloride than solvent B. In this context, it issubmitted that it is within the expert knowledge of a person skilled inthe art, to identify from the alcohols described herein as solvent Cthose alcohols which provide lower solubility to 4′-epidaunorubinhydrochloride than solvent B. For example, the skilled person maydissolve 4′-epidaunorubin hydrochloride in a solvent selected from thegroup consisting of C₁-C₅ straight and branched alcohols and mixturesthereof, and determine the dissolution capacity of this solvent for4′-epidaunorubin hydrochloride. In a next step, the skilled person maydissolve 4′-epidaunorubin hydrochloride in a different solvent selectedfrom the group consisting of C₁-C₅ straight and branched alcohols andmixtures thereof, and determine the dissolution capacity of this solventfor 4′-epidaunorubin hydrochloride. From the two kinds of solventsexamined, the skilled person designates as solvent B the alcohol(s) inwhich the solubility of 4′-epidaunorubin hydrochloride is higher.Accordingly, he designates as solvent C the alcohol(s) in which thesolubility of 4′-epidaunorubin hydrochloride is lower. Every alcoholhaving a C₁-C₅ carbon skeleton can be used as solvent C as long as it isable to act as an antisolvent to 4′-epidaunorubicin hydrochloride. Forexample, solvent C can be a monoalcohol or a polyalcohol. Furthermore,solvent C includes alcohols having further functional groups in additionto the hydroxyl group(s). It may be preferred, however, that solvent Bhave no further functional groups. Furthermore, it may be preferred thatsolvent C is a saturated compound and therefore does not contain doubleor triple bonds. According to a preferred embodiment, solvent C isselected from the group consisting of C₃-C₅ straight and branchedalcohols and mixtures thereof. According to a further preferredembodiment, solvent C is selected from the group consisting of C₃branched alcohols, C₄ straight and branched alcohols, C₅ straight andbranched alcohols, and mixtures thereof. Most preferably, solvent C isselected from the group consisting of isopropanol, 1-butanol, 2-butanoland 1-pentanol.

According to a preferred embodiment, the solvent system of the presentinvention comprises 0.1-20% by volume of solvent A, 7-50% by volume ofsolvent B and 45-92% by volume of solvent C.

According to another preferred embodiment, the solvent system comprises1-6% by volume of solvent A, 10-40% by volume of solvent B and 54-89% byvolume of solvent C.

It can furthermore be preferred that the solvent system is devoid ofsolvents other than solvents A, B or C. According to this embodiment,the solution does not contain solvents apart from solvents A, B and C.However, the solvent system is allowed to contain, apart from4′-epidaunorubicin hydrochloride, other ingredients, such as forexample, salts.

According to another preferred embodiment, the solvent system consistsof 4′-epidaunorubicin hydrochloride, and solvents A, B and C. In thiscase, no further ingredients are allowed to be present in the solventsystem.

The process of the present invention is preferably performed bydissolving 4′-epidaunorubicin hydrochloride in a solvent mixture I and,subsequently, contacting the resulting solution of 4′-epidaunorubicinhydrochloride with a solvent mixture II.

Solvent mixture I is characterized in comprising solvent A and havingthe capability to dissolve 4′-epidaunorubicin hydrochloride. Solventmixture I is also allowed to consist only of solvent A. In this case,however, solvent mixture II must comprise solvents B and C.Nevertheless, it is preferred that solvent mixture I comprises, inaddition to solvent A, also solvent B or solvent C, or a mixture ofsolvents B and C. In this case, it is preferred that solvent mixture Icomprises (i) solvent A, on the one hand, and (ii) solvent B or C or amixture thereof, on the other hand, in a volume ratio between 1:2 and4:1. Preferably, the volume ratio between (i) solvent A and (ii) solventB, C or a mixture thereof, is between 0.75:1 and 3:1, and mostpreferably between 1:1 and 2:1.

Solvent mixture II comprises solvent C. Solvent system II is generallyallowed to consist only of solvent C. In this case, however, solventmixture I has to comprise solvent A and solvent B. According to apreferred embodiment, solvent mixture II comprises solvents B and C.

Solvent mixture I is able to dissolve 4′-epidaunorubicin hydrochloride.Accordingly, in a first step of the process of the present invention,4′-epidaunorubicin hydrochloride is dissolved completely in solventmixture I. If necessary, one can assist in dissolving 4′-epidaunorubicinhydrochloride in solvent mixture I by increasing the temperature ofsolvent mixture I. For example, dissolution of 4′-epidaunorubicinhydrochloride in solvent mixture I can be performed at a temperature inthe range between 40-80° C., preferably between 50-70° C., and mostpreferably between 55 and 65° C. Preferably, heating of solvent mixtureI is accompanied by stirring.

Subsequently, the solution of 4′-epidaunorubicin hydrochloride insolvent mixture I is contacted with solvent mixture II. Therefore,solvent mixture II can be added to the solution of 4′-epidaunorubicinhydrochloride in solvent mixture I. On the other hand, it is alsopossible to add the solution of 4′-epidaunorubicin hydrochloride insolvent mixture I to solvent mixture II. The solvent mixtures can bebrought into contact by every conceivable means. For example, it ispossible to drop, inject or pour the 4′-epidaunorubicinhydrochloride-containing solvent mixture I in solvent mixture II or viceversa. Preferably, the solvent mixtures are brought into contact byslowly dropping the 4′-epidaunorubicin hydrochloride-containing solventmixture I in solvent mixture II or vice versa. Dropping can beperformed, for example, for a period of 1 second to 1 hour, such as 1minute to 40 minutes, or 5 minutes to 30 minutes.

According to a preferred embodiment, upon contact of the solution of4′-epidaunorubicin hydrochloride in solvent mixture I with solventmixture II, the resulting solvent system comprises 0.1-20% by volume,preferably 0.1-15% by volume, more preferably 0.1-12% by volume, andmost preferably 0.1-10% by volume, of solvent A.

By reducing the concentration of solvent A by means of contact withsolvent mixture II not containing solvent A, solubility of4′-epidaunorubicin hydrochloride is reduced. When the concentration ofsolvent A in the solvent system decreases below 20% by volume,preferably below 15% by volume, more preferably below 12% by volume, andmost preferably below 10% by volume, crystallization of4′-epidaunorubicin hydrochloride is initiated under suitable conditions.In this context, however, it has been found that decreasing theconcentration of solvent A below a certain level is not sufficient tocause crystallization. It is essential that the solvent(s) used fordiluting solvent A and thus to reduce the concentration of solvent A inthe solvent mixture is (are) suitable solvent(s). In particular, it hasbeen found that contacting the solution of 4′-epidaunorubicinhydrochloride in solvent A with conventionally used antisolvents, suchas ethers, ketones, esters, and nitriles causes sudden precipitation of4′-epidaunorubicin hydrochloride. In this case, amorphous4′-epidaunorubicin hydrochloride is precipitated, which has thedrawbacks mentioned above. Therefore, it is essential that the solutionof 4′-epidaunorubicin hydrochloride in solvent A be contacted withsolvent C. Solvent C contains a suitable alcohol which has been found toreadily interact with the polar functional groups of 4′-epidaunorubicinhydrochloride. Therefore, slow crystallization instead of suddenprecipitation is caused, resulting in the production of crystalline4′-epidaunorubicin hydrochloride.

For further optimization of this process, the concentration of4′-epidaunorubicin hydrochloride in the solvent system is adjusted tobetween 7 g/l and 30 g/l, preferably between 7.5 g/l and 25 g/l, andmost preferably between 8 g/l and 20 g/l.

It is furthermore preferred that the pH value of the 4′-epidaunorubicinhydrochloride-containing solvent system be in a range between pH 2-5.

Furthermore, according to another preferred embodiment, after contactingthe solution of 4′-epidaunorubicin hydrochloride with solvent mixtureII, the resulting mixture is cooled to a temperature in the rangebetween 5-35° C., preferably 15-30° C., and most preferably 20-30° C.

According to another preferred embodiment, the resulting mixture iscooled to a temperature in the range between 5-35° C., preferably 15-30°C. and most preferably 20-30° C., within a period of 2-8, preferably 3-7and more preferably 4-6 hours, starting from the time of contact ofsolvent mixture I with solvent mixture II.

According to another preferred embodiment, the resulting mixture isstirred at a temperature in the range between 5-35° C., preferably15-30° C. and most preferably 20-30° C., for a period of 2-24 hours,preferably 4-20 hours, more preferably 8-16 hours, even more preferably10-14 hours.

Crystalline 4′-epidanunorubicin hydrochloride obtained by carrying outthe process of the present invention preferably has the powder X-raydiffraction pattern as defined in Table 1. The powder X-ray diffractionpattern is preferably measured using Kα₁ radiation; the STOE STADI PPOWDER DIFFRACTION SYSTEM (Stoe CIE GmbH, Darmstadt, Germany) ispreferably used as the measuring device.

TABLE 1 Powder X-ray diffraction pattern of 4′-epidaunorubicinhydrochloride crystals according to a preferred embodiment of thepresent invention. Diffraction Angle 2 (theta) Relative intensity P (%)4.98 15.00-17.00 5.13 40.00-46.00 7.23 15.90-17.20 7.64 29.00-33.5011.37 7.00-8.00 12.01 10.90-11.50 12.18 23.50-26.00 16.18 8.50-9.8016.77 18.90-20.70 17.00 24.50-26.90 18.46  9.00-10.00 18.75 6.80-7.3019.24 10.80-12.00 19.86 54.00-62.00 20.22 16.70-18.10 21.21 6.90-7.5021.82 25.80-28.25 22.58 100 23.03 30.00-32.00 23.44 14.00-15.00 24.53 9.3-10.60 26.55 8.00-9.50 26.86 13.40-14.60 30.59 8.65-9.45 32.36 9.70-10.70 34.82 6.60-7.40

Crystalline 4′-epidanorubicin hydrochloride of the present inventionmore preferably has the powder X-ray diffraction pattern as defined inTable 2. The data of Table 2 are preferably obtained with the STOE STADIP POWDER DIFFRACTION SYSTEM (Stoe CIE GmbH, Darmstadt, Germany) usingKα₁ radiation:

TABLE 2 More preferred powder X-ray diffraction pattern of4′-epidaunorubicin hydrochloride crystals as obtained in accordance withthe present invention. Diffraction Angle 2 (theta) Relative intensity P(%) 4.98 15.90 5.13 43.50 7.23 16.61 7.64 31.66 11.37 7.57 12.01 11.2312.18 24.62 16.18 9.17 16.77 19.74 17.00 25.61 18.46 9.60 18.75 7.0819.24 11.46 19.86 58.23 20.22 17.36 21.21 7.21 21.82 26.94 22.58 10023.03 31.12 23.44 14.55 24.53 9.94 26.55 8.75 26.86 14.19 30.59 9.0932.36 10.30 34.82 7.03

According to an even more preferred embodiment, crystalline4′-epidaunorubicin hydrochloride of the present invention has one, moreor all of the powder X-ray diffraction values (particular range ofrelative intensity at a particular diffraction angle 2(theta)) outlinedin Table 3 as preferably measured with the STOE STADI P POWDERDIFFRACTION SYSTEM (Stoe CIE GmbH, Darmstadt, Germany) using Kα₁radiation:

TABLE 3 Powder X-ray diffraction pattern of 4′-epidaunorubicinhydrochloride crystals according to an even more preferred embodiment ofthe present invention. Diffraction Angle 2 (theta) Relative intensity P(%) 5.13 40.00-46.00 7.64 29.00-33.50 12.18 23.50-26.00 16.7718.90-20.70 17.00 24.50-26.90 19.86 54.00-62.00 21.82 25.80-28.25 22.58100 23.03 30.00-32.00

Crystalline 4′-epidaunorubicin hydrochloride produced according to theprocess described herein can have the physical parameters as shown inTable 4. These data were obtained in single X-ray analysis using aninstrument of Xcalibur Oxford Diffraction and MoKa (0.7107 mm⁻¹) asradiation source.

TABLE 4 Data of single X-ray analysis of 4′-epidaunorubicinhydrochloride as obtained in accordance with the present invention.Compound [4′-epidaunorubicin]HCl Crystal color and habit Red prismsCrystal size (mm) 0.2 × 0.2 × 0.1 Crystal system Monoclinic Space groupP21 Lattice constant a (Å) 16.5070 (11) Lattice constant b (Å) 5.4290(4) Lattice constant c (Å) 16.9178 (9)  Lattice angle α (°) 90 Latticeangle β (°) 93.164 (5) Lattice angle γ (°) 90 Volume V (Å³) 1513.80 (17)Density ρ_(calc) (g × cm⁻³) 1.336 ⊖ range (°) 2.41-29.05

The process of the present invention allows for the production ofcrystalline 4′-epidaunorubicin hydrochloride having high purity,improved solubility in methanol and high thermal stability. In a singleX-Ray analysis, the crystalline 4′-epidaunorubicin hydrochlorideproduced according to the process of the present invention preferablyhas monoclinic crystal structure. In the monoclinic system, the crystalis described by vectors of unequal length, as in the orthorhombicsystem. They form a rectangular prism with a parallelogram at its base.Hence, two pairs of vectors are perpendicular, while the third pairmakes an angle other than 90°.

Therefore, the present invention provides crystalline 4′-epidaunorubicinhydrochloride which preferably has a monoclinic phase content of atleast 10%. According to further preferred embodiments, the monoclinicphase content of the crystalline 4′-epidaunorubicin hydrochloride is atleast 20%, at least 30%, at least 40%, at least 50%, at least 60%, atleast 70%, at least 80%, at least 90%, at least 95% or at least 99%.According to a particular preferred embodiment, the crystalline4′-epidaunorubicin hydrochloride consists only of the monoclinic form.It is further preferred that the crystalline 4′-epidaunorubicinhydrochloride of the present invention does not form part of a complexwith other molecules, for example DNA, RNA or proteins.

The crystalline 4′-epidaunorubicin hydrochloride of the presentinvention excels in purity and shows improved solubility, in particular,in methanol. Therefore, it can be beneficially used in downstreamprocesses for the production of anthracyclines. For example, crystalline4′-epidaunorubicin hydrochloride can be used to produce epirubicin. Theprocess for producing epirubicin from 4′-epidaunorubicin hydrochlorideas a starting material is well-known in the art. Because of its highpurity and good solubility in methanol, the use of crystalline4′-epidaunorubicin hydrochloride as a starting material for thesynthesis of epirubicin is beneficial over the use of amorphous4′-epidaunorubicin hydrochloride.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following figures provide supplementary information on the4′-epidaunorubicin hydrochloride as produced according to the presentinvention:

FIG. 1 is a molecular model showing the stereochemistry of4′-epidaunorubicin hydrochloride according to single X-Ray data; and

FIG. 2 is a graph showing the thermogravimetric analysis (TGA) of4′-epidaunorubicin hydrochloride. The data were obtained using theinstrument NETZSCH TG 209 (sample mass: 12.917 g, range: 24.0/10.0(K/min)/250.0, crucible: Al₂O₃).

DETAILED DESCRIPTION OF THE INVENTION

The present invention is hereinafter described by way of Examples.

Example 1

10 g 4′-epidaunorubicin hydrochloride were dissolved in a mixture ofchloroform and butanol (ratio=2:1 by volume). To this mixture, 10-timesthe volume of a mixture of 1-propanol and 1-butanol (ratio=3:7 byvolume) was added at 60° C. The end concentration of 4′-epidaunorubicinhydrochloride in the resulting solvent system was 8 g/l.

The mixture was cooled to room temperature within a period of 5 hours,and subsequently stirred for 12 hr at room temperature.

The resulting crystals were separated from the solvent mixture by meansof filtration, washed with 50 ml tert-butyl-methylether and dried atvacuum (<400 mbar).

The crystals were analyzed and confirmed as 4′-epidaunorubicinhydrochloride. The yield was 9.2 g, the purity was 98.2%. The productdecomposed at 191° C., the mass was 528 D.

Example 2

10 g 4′-epidaunorubicin hydrochloride were dissolved in a mixture ofchloroform and butanol (ratio=2:1 by volume). This mixture was slowlyadded to 10-times the volume of a mixture of 1-propanol and 1-butanol(ratio=3:7 by volume) at 60° C. The end concentration of4′-epidaunorubicin hydrochloride in the resulting solvent system was 20g/l.

The mixture was cooled to room temperature within a period of 5 hours,and subsequently stirred for 12 hr at room temperature.

The resulting crystals were separated from the solvent mixture by meansof filtration, washed with 50 ml tert-butyl-methylether and dried atvacuum (<400 mbar).

The crystals were analyzed and confirmed as 4′-epidaunorubicinhydrochloride. The yield was 9.2 g, the purity was 98.2%. The productdecomposed at 191° C., the mass was 528 D.

Example 3

10 g 4′-epidaunorubicin hydrochloride were dissolved in a mixture ofdichloromethane and 1-propanol (ratio=1:1 by volume). To this mixture,10-times the volume of a mixture of 1-propanol and isopropanol(ratio=2.5:8 by volume) was slowly added at 60° C. The end concentrationof 4′-epidaunorubicin hydrochloride in the resulting solvent system was8 g.

The mixture was cooled to room temperature within a period of 5 hours,and subsequently stirred for 12 hr at room temperature.

The resulting crystals were separated from the solvent mixture by meansof filtration, washed with 50 ml tert-butyl-methylether and dried atvacuum (<400 mbar).

The crystals were analyzed and confirmed as 4′-epidaunorubicinhydrochloride. The yield was 9.1 g, the purity was 98.0%. The productdecomposed at 190° C., the mass was 528 D.

Example 4

10 g 4′-epidaunorubicin hydrochloride were dissolved in a mixture ofdichloromethane and 1-propanol (ratio=1:1 by volume). To this mixture,10-times the volume of a mixture of 1-propanol and isopropanol(ratio=2.5:8 by volume) was slowly added at 60° C. The end concentrationof 4′-epidaunorubicin hydrochloride in the resulting solvent system was20 g.

The mixture was cooled to room temperature within a period of 5 hours,and subsequently stirred for 12 hr at room temperature.

The resulting crystals were separated from the solvent mixture by meansof filtration, washed with 50 ml tert-butyl-methylether and dried atvacuum (<400 mbar).

The crystals were analyzed and confirmed as 4′-epidaunorubicinhydrochloride. The yield was 9.1 g, the purity was 98.0%. The productdecomposed at 190° C., the mass was 528 D.

Comparative Example 1

4′-epidaunorubicin hydrochloride was produced and purified (by addingmethanolic hydrogen chloride to a chloroform extract of4′-epidaunorubicin hydrochloride) according to Example 2 of U.S. Pat.No. 4,345,068. As a result, 4′-epidaunorubicin hydrochloride wasobtained and precipitated as an amorphous powder.

Comparative Example 2

4′-epidaunorubicin hydrochloride was produced and purified (by addingmethanolic hydrogen chloride to a chloroform extract of4′-epidaunorubicin hydrochloride) according to Example 5 of U.S. Pat.No. 4,345,068. As a result, 4′-epidaunorubicin hydrochloride wasobtained and precipitated as an amorphous powder.

Comparative Example 3

4′-epidaunorubicin hydrochloride was produced and purified (by usingethanol/ether) according to Boivin et al., “Substitutions of allylicesters: preparation of 3-aminoglycals and their acid-catalyzedglycosidation. Use in the partial synthesis of glycosides of theanthracycline group,” Carbohydrate Research, 79 (2): 193-204 (1980). Asa result, 4′-epidaunorubicin hydrochloride was obtained and precipitatedas an amorphous powder.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

We claim:
 1. A process for producing crystalline 4′-epidaunorubicinhydrochloride comprising crystallizing 4′-epidaunorubicin hydrochloridein a solvent system including: a) solvent A which is selected from thegroup consisting of C₁ and C₂ halogenated solvents and mixtures thereof;b) solvent B which is selected from the group consisting of C₁-C₅straight and branched alcohols and mixtures thereof; and c) solvent Cwhich is selected from the group consisting of C₁-C₅ straight andbranched alcohols and mixtures thereof, wherein solvent C is selected toprovide lower solubility to 4′-epidaunorubicin hydrochloride thansolvent B, wherein the process comprises steps of: dissolving4′-epidaunorubicin hydrochloride in a solvent mixture I comprising (i)solvent A and (ii) solvent B or C to form a solution; and contacting thesolution with a solvent mixture II comprising solvents B and C.
 2. Theprocess according to claim 1, wherein the solvent system comprises0.1-20% by volume of solvent A, 7-50% by volume of solvent B and 45-92%by volume of solvent C.
 3. The process according to claim 2, wherein thesolvent system comprises 1-6% by volume of solvent A, 10-40% by volumeof solvent B and 54-89% by volume of solvent C.
 4. The process accordingto claim 1, wherein solvent mixture I comprises (i) solvent A and (ii)solvent B or C in a volume ratio between 1:2 and 4:1.
 5. The processaccording to claim 1, wherein upon contacting solvent mixture I withsolvent mixture II, the solvent system comprises 0.1-20% by volume ofsolvent A.
 6. The process according to claim 1, wherein a concentrationof 4′-epidaunorubicin hydrochloride in the solvent system is between 7g/l and 30 g/l.
 7. The process according to claim 1, wherein dissolutionof 4′-epidaunorubicin hydrochloride in solvent mixture I is performed ata temperature in the range between 40-80° C.
 8. The process according toclaim 7, wherein after contacting the solution of 4′-epidaunorubicinhydrochloride with solvent mixture II the resulting mixture is cooled toa temperature in the range of 5-35° C.
 9. The process according to claim1, wherein solvent A is selected from the group consisting of chloroformand dichloromethane.
 10. The process according to claim 1, whereinsolvent B is selected from the group consisting of methanol, ethanol and1-propanol.
 11. The process according to claim 1, wherein solvent C isselected from the group consisting of 1-butanol, isopropanol,isobutanol, and 1-pentanol.
 12. The process according to claim 1,wherein the solvent system consists of solvents A, B and C.